Transit detections of extrasolar planets around main-sequence stars - I. Sky maps for hot Jupiters

Abstract

The findings of more than 350 extrasolar planets, most of them nontransiting Hot Jupiters, have revealed correlations between the metallicity of the main-sequence (MS) host stars and planetary incidence. This connection can be used to calculate the planet formation probability around other stars, not yet known to have planetary companions. We locate the promising spots for current transit surveys on the celestial plane and strive for absolute values of the expected number of transits in general. We used data of the Tycho catalog for about 1 million objects to locate all the stars with 0m < m_V < 11.5m on the celestial plane. We took several empirical relations between the parameters listed in the Tycho catalog, such as distance to Earth, m_V, and (B-V), and those parameters needed to account for the probability of a star to host an observable, transiting exoplanet. The empirical relations between stellar metallicity and planet occurrence combined with geometrical considerations were used to yield transit probabilities for the MS stars in the Tycho catalog. Magnitude variations in the FOV were simulated to test whether this fluctuations would be detected by BEST, XO, SuperWASP and HATNet. We present a sky map of the expected number of Hot Jupiter transit events on the basis of the Tycho catalog. The comparison between the considered transit surveys yields significantly differing maps of the expected transit detections. The sky-integrated magnitude distribution predicts 20 Hot Jupiter transits with orbital periods between 1.5 d and 50 d and m_V < 8m, of which two are currently known. In total, we expect 3412 Hot Jupiter transits to occur in front of MS stars within the given magnitude range. The most promising observing site on Earth is at latitude = -1.